Author Topic: DC Load - I need some guidance  (Read 4507 times)

0 Members and 1 Guest are viewing this topic.

Offline nctnico

  • Super Contributor
  • ***
  • Posts: 28429
  • Country: nl
    • NCT Developments
Re: DC Load - I need some guidance
« Reply #25 on: June 13, 2024, 09:29:13 pm »
I've been working with it a bit, it's making a good impression so far - but I'll do a proper test with it when time finally allows and post it in the forum.
I have all the resources for it, I still have to get a battery, if you want to determine the ripple of the load, a regulated power supply makes little sense as a source.
When I have that, I'll get started.
Well, for 50Hz ripple, a decent power supply should have a low enough ripple & output impedance to test. It would be interesting to know whether the Siglent loads have the 50Hz current ripple or not.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline Martin72

  • Super Contributor
  • ***
  • Posts: 7019
  • Country: de
  • Testfield Technician
Re: DC Load - I need some guidance
« Reply #26 on: June 13, 2024, 10:05:04 pm »
We will see.
My fear is that when two regulated systems "meet", this can lead to interactions.
I also have a few linear "iron" power supply units, but they can only handle a maximum load of 3A, which is not a lot.

Offline nctnico

  • Super Contributor
  • ***
  • Posts: 28429
  • Country: nl
    • NCT Developments
Re: DC Load - I need some guidance
« Reply #27 on: June 13, 2024, 10:13:50 pm »
We will see.
My fear is that when two regulated systems "meet", this can lead to interactions.
I also have a few linear "iron" power supply units, but they can only handle a maximum load of 3A, which is not a lot.
You won't need a lot of current to show the DC load regulation ripple. 100mA is more than enough; otherwise you'd likely be swamping the ripple you want to measure.
« Last Edit: June 13, 2024, 10:18:51 pm by nctnico »
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 
The following users thanked this post: Martin72

Offline mvno_subscriberTopic starter

  • Regular Contributor
  • *
  • Posts: 91
  • Country: no
Re: DC Load - I need some guidance
« Reply #28 on: June 14, 2024, 06:19:48 am »
I got the unit yesterday. I won't be able to test it properly before next week, but wanted to hook it up and just fiddle around a bit. Now, two things struck me, one of which I'm not sure what to do with.

1. The fan is always on. It's not super loud. It's a bit quieter than my oscilloscope (Rigol). It sucks, but I'll probably be able to live with it. Most likely I'll have my scope powered up whenever I use this thing anyway.

2. There's a really high pitched noise coming from the unit. It's higher than your average CRT monitor whine. It's almost not a sound at all, and more a sensation. It's very fatiguing, almost nauseating. I downloaded a random FFT app on my phone, it registered a 15Khz spike at startup (which is clearly audible, sounds like something charging up), but then nothing. The nauseating sound has higher pitch than that, how much higher I'm not sure, but I assume it has to be quite loud for me to actually hear it. I mean, I guess I have a good ear, but I am 41 and have no illusions :D

I hope then that this whine is a fault, or that it will pass (is it possible?). If not, I'm not sure if I'll be able to live with it. Crossing my fingers 🤞🤞
 

Offline 2N3055

  • Super Contributor
  • ***
  • Posts: 7466
  • Country: hr
Re: DC Load - I need some guidance
« Reply #29 on: June 14, 2024, 07:41:00 am »
I got the unit yesterday. I won't be able to test it properly before next week, but wanted to hook it up and just fiddle around a bit. Now, two things struck me, one of which I'm not sure what to do with.

1. The fan is always on. It's not super loud. It's a bit quieter than my oscilloscope (Rigol). It sucks, but I'll probably be able to live with it. Most likely I'll have my scope powered up whenever I use this thing anyway.

2. There's a really high pitched noise coming from the unit. It's higher than your average CRT monitor whine. It's almost not a sound at all, and more a sensation. It's very fatiguing, almost nauseating. I downloaded a random FFT app on my phone, it registered a 15Khz spike at startup (which is clearly audible, sounds like something charging up), but then nothing. The nauseating sound has higher pitch than that, how much higher I'm not sure, but I assume it has to be quite loud for me to actually hear it. I mean, I guess I have a good ear, but I am 41 and have no illusions :D

I hope then that this whine is a fault, or that it will pass (is it possible?). If not, I'm not sure if I'll be able to live with it. Crossing my fingers 🤞🤞

That whine is either coming from PWM for fan or from a switcher PSU. If it is there it won't get tired and go somewhere else....
"Just hard work is not enough - it must be applied sensibly."
Dr. Richard W. Hamming
 
The following users thanked this post: mvno_subscriber

Offline mvno_subscriberTopic starter

  • Regular Contributor
  • *
  • Posts: 91
  • Country: no
Re: DC Load - I need some guidance
« Reply #30 on: June 14, 2024, 07:56:46 am »
That whine is either coming from PWM for fan or from a switcher PSU. If it is there it won't get tired and go somewhere else....

Is there anything I can do to dampen it without meddling with its insides? Could it be its placement somehow acoustically amplifies the sound? I find it difficult to imagine that this is how it's supposed to be.
 

Offline 2N3055

  • Super Contributor
  • ***
  • Posts: 7466
  • Country: hr
Re: DC Load - I need some guidance
« Reply #31 on: June 14, 2024, 08:10:16 am »
That whine is either coming from PWM for fan or from a switcher PSU. If it is there it won't get tired and go somewhere else....

Is there anything I can do to dampen it without meddling with its insides? Could it be its placement somehow acoustically amplifies the sound? I find it difficult to imagine that this is how it's supposed to be.

I don't know. First you need to realize where is comes from.
If it comes from fan PWM, you have actual fan being a speaker....
It might change as fan RPM change.

If it comes from PSU, then it is some component that is making a noise. A inductor, transformer or something else magnetostrictive or piezoelectric (like ceramic capacitors for instance)..

It might as well be a standard thing on these.
« Last Edit: June 14, 2024, 08:17:28 am by 2N3055 »
"Just hard work is not enough - it must be applied sensibly."
Dr. Richard W. Hamming
 
The following users thanked this post: mvno_subscriber

Offline mvno_subscriberTopic starter

  • Regular Contributor
  • *
  • Posts: 91
  • Country: no
Re: DC Load - I need some guidance
« Reply #32 on: June 14, 2024, 06:39:44 pm »


I don't know. First you need to realize where is comes from.
If it comes from fan PWM, you have actual fan being a speaker....
It might change as fan RPM change.

If it comes from PSU, then it is some component that is making a noise. A inductor, transformer or something else magnetostrictive or piezoelectric (like ceramic capacitors for instance)..

It might as well be a standard thing on these.

Tried loading it with 150W to make the fans spin up, and spin up they did. Still the same whining, though. Had ringing in my ears 15 minutes after I turned it off. I'll call for a replacement unit on monday, this has to be defective. Right now it's a health hazard.

That said, I really like it so far and I don't want to let it go. It has already gotten a place in my heart! Let's hope a new unit will fix things.
 
The following users thanked this post: 2N3055, BILLPOD

Offline Martin72

  • Super Contributor
  • ***
  • Posts: 7019
  • Country: de
  • Testfield Technician
Re: DC Load - I need some guidance
« Reply #33 on: June 15, 2024, 10:44:17 pm »
Quote
If it comes from PSU, then it is some component that is making a noise. A inductor, transformer or something else magnetostrictive or piezoelectric (like ceramic capacitors for instance)..

These are usually inductors such as core chokes or transformers.
The wire windings are relatively loose around the core and start to vibrate when current flows, this is transferred to the core and the whole thing forms a small "loudspeaker".
We impregnate our coils/transformers under vacuum, which reduces the vibrations enormously.
What you can do "privately" and afterwards is to localize the sounding component and cover it with e.g. silicone.
 
The following users thanked this post: egonotto, mvno_subscriber

Offline 2N3055

  • Super Contributor
  • ***
  • Posts: 7466
  • Country: hr
Re: DC Load - I need some guidance
« Reply #34 on: June 15, 2024, 11:08:04 pm »
Quote
If it comes from PSU, then it is some component that is making a noise. A inductor, transformer or something else magnetostrictive or piezoelectric (like ceramic capacitors for instance)..

These are usually inductors such as core chokes or transformers.
The wire windings are relatively loose around the core and start to vibrate when current flows, this is transferred to the core and the whole thing forms a small "loudspeaker".
We impregnate our coils/transformers under vacuum, which reduces the vibrations enormously.
What you can do "privately" and afterwards is to localize the sounding component and cover it with e.g. silicone.

I also have heard elkos and ceramic capacitors "sing" quite nicely...
"Just hard work is not enough - it must be applied sensibly."
Dr. Richard W. Hamming
 
The following users thanked this post: egonotto

Offline DaneLaw

  • Frequent Contributor
  • **
  • Posts: 661
  • Country: dk
Re: DC Load - I need some guidance
« Reply #35 on: June 15, 2024, 11:12:45 pm »
Shame with the whine, as it is such relative things that one would expect are sorted out the more expensive units from certain brands - Tonghui rebadge or not.
Where did you purchase it from? did it seem new when it arrived (like you were the first unboxing it) if not, it could indicate that its solely this unit, and some other buyer has been there with a "no thx, you're going back" and the reseller is trying their luck to find it a new home.

Are the 4mm protruding input jacks on BK8550 of the 8mm grade with 2mm wall-thickness or is it the 6mm that are common on many power supplies with 1mm thickness?
On East Testers programmable loads, it looks  to vary depending on wattage and could look like its the 6mm wide/1mm metalthickness on ET5420 (2ch 20A pr. channel / ET5411 1ch 500V/15A) while 8mm/2mm metal-thickness on the 40A  load (ET5410). https://cdn.globalso.com/easttester-cn/fu3.jpg

BK8550/TH8401 does look good, kudos for both sense & 4mm input jacks at the front.
 
The following users thanked this post: egonotto

Offline mvno_subscriberTopic starter

  • Regular Contributor
  • *
  • Posts: 91
  • Country: no
Re: DC Load - I need some guidance
« Reply #36 on: June 16, 2024, 12:11:16 pm »
Where did you purchase it from? did it seem new when it arrived (like you were the first unboxing it) if not, it could indicate that its solely this unit, and some other buyer has been there with a "no thx, you're going back" and the reseller is trying their luck to find it a new home.

Are the 4mm protruding input jacks on BK8550 of the 8mm grade with 2mm wall-thickness or is it the 6mm that are common on many power supplies with 1mm thickness?
On East Testers programmable loads, it looks  to vary depending on wattage and could look like its the 6mm wide/1mm metalthickness on ET5420 (2ch 20A pr. channel / ET5411 1ch 500V/15A) while 8mm/2mm metal-thickness on the 40A  load (ET5410). https://cdn.globalso.com/easttester-cn/fu3.jpg

BK8550/TH8401 does look good, kudos for both sense & 4mm input jacks at the front.

I bought it from Elfa Distrelec. Funny you should mention if it had been a return item, I did wonder if it had been opened before when I unpackaged it, there was something.. but everything seemed well packed inside.

Regarding the banana jacks, I wasn't quite sure I understood the question, but with threads the outer diameter is 8mm (see pic). Feels pretty solid.

The knob that is screwed on also feels decent. Weighs in at 27g on my generic kitchen scale.
 

Offline Martin72

  • Super Contributor
  • ***
  • Posts: 7019
  • Country: de
  • Testfield Technician
Re: DC Load - I need some guidance
« Reply #37 on: June 16, 2024, 12:26:54 pm »
Every DC load or power supply unit should have such combined 4mm/screw terminals.
 
The following users thanked this post: nctnico, egonotto

Offline mvno_subscriberTopic starter

  • Regular Contributor
  • *
  • Posts: 91
  • Country: no
Re: DC Load - I need some guidance
« Reply #38 on: June 16, 2024, 06:31:36 pm »
I wonder if something else is up with this unit. On the back, it has a BNC out to connect a scope. From the manual: "Connect an external voltmeter or oscilloscope to display the input’s current."

I've never used such a feature before and I couldn't find anywhere what it's supposed to read, but I assumed maybe 1V per amp or something? Anyway, its output is a third of that; 333mV per amp (on scope set to 1X = 1M input impedance). Is that normal? I've tried two different cables, same result, and double checked that my scope is not defunct.

Am I doing it wrong?
 

Offline nctnico

  • Super Contributor
  • ***
  • Posts: 28429
  • Country: nl
    • NCT Developments
Re: DC Load - I need some guidance
« Reply #39 on: June 16, 2024, 06:37:12 pm »
I wonder if something else is up with this unit. On the back, it has a BNC out to connect a scope. From the manual: "Connect an external voltmeter or oscilloscope to display the input’s current."

I've never used such a feature before and I couldn't find anywhere what it's supposed to read, but I assumed maybe 1V per amp or something? Anyway, its output is a third of that; 333mV per amp (on scope set to 1X = 1M input impedance). Is that normal? I've tried two different cables, same result, and double checked that my scope is not defunct.
The Tonghui manual says it is a 0V to 10V output with 10V being full scale. So if the range (full scale) is 30A then the output will be 10/30 = 333.3mV/A which is exactly what you are measuring.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 
The following users thanked this post: mvno_subscriber

Offline mvno_subscriberTopic starter

  • Regular Contributor
  • *
  • Posts: 91
  • Country: no
Re: DC Load - I need some guidance
« Reply #40 on: June 16, 2024, 06:49:01 pm »
It shows 333mA regardless of range (3A/30A). But clearly, 333mV per amp. I guess that's ok then. Is such a weird scale common on these kinds of instruments?
 

Offline nctnico

  • Super Contributor
  • ***
  • Posts: 28429
  • Country: nl
    • NCT Developments
Re: DC Load - I need some guidance
« Reply #41 on: June 16, 2024, 07:15:49 pm »
It shows 333mA regardless of range (3A/30A). But clearly, 333mV per amp. I guess that's ok then. Is such a weird scale common on these kinds of instruments?
0V to 10V is a common output range for monitoring / control purposes. But you can choose a custom probe attenuation factor to compensate on an oscilloscope. More advanced multimeters also allow to use math to scale a reading.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline Martin72

  • Super Contributor
  • ***
  • Posts: 7019
  • Country: de
  • Testfield Technician
Re: DC Load - I need some guidance
« Reply #42 on: June 16, 2024, 09:06:15 pm »
I also have heard elkos and ceramic capacitors "sing" quite nicely...
With ceramic capacitors, you can try to replace them with MIL types - under no circumstances should you blindly replace them with supposedly better film types.
"Singing" electrolytic capacitors:
Anyone who has always wondered why many (switching) power supplies have their electrolytic capacitors glued to a mostly white viscous mass, well this is the reason.
 
The following users thanked this post: egonotto, 2N3055

Offline DaneLaw

  • Frequent Contributor
  • **
  • Posts: 661
  • Country: dk
Re: DC Load - I need some guidance
« Reply #43 on: June 16, 2024, 10:35:22 pm »
Where did you purchase it from? did it seem new when it arrived (like you were the first unboxing it) if not, it could indicate that its solely this unit, and some other buyer has been there with a "no thx, you're going back" and the reseller is trying their luck to find it a new home.

Are the 4mm protruding input jacks on BK8550 of the 8mm grade with 2mm wall-thickness or is it the 6mm that are common on many power supplies with 1mm thickness?
On East Testers programmable loads, it looks  to vary depending on wattage and could look like its the 6mm wide/1mm metalthickness on ET5420 (2ch 20A pr. channel / ET5411 1ch 500V/15A) while 8mm/2mm metal-thickness on the 40A  load (ET5410). https://cdn.globalso.com/easttester-cn/fu3.jpg

BK8550/TH8401 does look good, kudos for both sense & 4mm input jacks at the front.

I bought it from Elfa Distrelec. Funny you should mention if it had been a return item, I did wonder if it had been opened before when I unpackaged it, there was something.. but everything seemed well packed inside.

Regarding the banana jacks, I wasn't quite sure I understood the question, but with threads the outer diameter is 8mm (see pic). Feels pretty solid.

The knob that is screwed on also feels decent. Weighs in at 27g on my generic kitchen scale.

Yes, the circumference of the 4mm socket.
6mm -4mm = 1mm sides.
8mm - 4mm = 2mm sides.

If its  Elfa Distrelec Norway, then contact them and explain the whine-issue, and your concern if itis a brand-new unit, and you wanna return it for another..
One of the benefits of purchasing from local resellers.

 
The following users thanked this post: mvno_subscriber

Offline mvno_subscriberTopic starter

  • Regular Contributor
  • *
  • Posts: 91
  • Country: no
Re: DC Load - I need some guidance
« Reply #44 on: June 18, 2024, 09:46:57 am »
A quick update: I contacted Elfa yesterday, and today they're sending a replacement unit.

This is why I always buy big things from local sellers, even though it sometimes is a bit more expensive (which, in today's world, it seldom is anyway).

Crossing my fingers the new unit is better. Will come back to this thread when I've installed the new one.
 
The following users thanked this post: Martin72

Offline mvno_subscriberTopic starter

  • Regular Contributor
  • *
  • Posts: 91
  • Country: no
Re: DC Load - I need some guidance
« Reply #45 on: November 05, 2024, 08:33:09 am »
Realized I hadn't posted anything here; I haven't had the opportunity to test the load thoroughly enough. I've only used it for testing power supplies and discharging batteries so far.

What I can say is that, with regards to ripple, it self reports a ripple of about 5mVpp. When analyzing with a scope, it seems to be about 3-10mVpp depending on the circumstances. I suspect the last digit on the display of the load has limited precision.

Just thought someone might find it interesting.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf